It is conventional in the packaging field to provide pressurized closure and container packages, such as cold soft drink packages, having a flexible resilient liner for sealing engagement with at least one sealing surface on the container neck finish. Linerless closures have been proposed for non-pressurized packages to eliminate the expense of providing a sealing liner on the closure. However, linerless closures have not been as successful as desired in pressurized package applications, ranging from bottled water packages having an internal pressure of about 10 psi to cold soft drink packages having an internal pressure of about 75 psi at room temperature. Difficulties are encountered in manufacturing the closure with sufficient accuracy to maintain sealing contact with the container neck finish, particularly in applications involving molded plastic containers. It is a general object of the present disclosure to provide a linerless closure, and to provide a package embodying such a closure, that is adapted to achieve and maintain sealing engagement with the container neck finish in pressurized package applications over normal manufacturing tolerance variations on the closure and the container neck finish.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A linerless closure of one-piece integrally molded plastic construction, in accordance with one aspect of the present disclosure, includes a base wall and a cylindrical skirt for attaching the closure to a container neck finish. First and second circumferentially continuous annular walls extend from the base wall at positions radially inward from the skirt. The first and second annular walls are spaced from each other to receive an end portion of the container neck finish when the closure is applied to the neck finish. At least one of the annular walls has a circumferentially continuous annular projection extending toward the opposing annular wall. The annular projection is axially flexible for bending and folding toward the base wall and toward the at least one annular wall in sealing engagement with the end portion of the container neck finish when such end portion is received between the annular walls.
In exemplary preferred embodiments of the disclosure, the base wall has a central portion with a first thickness, a first peripheral portion contiguous with the central portion and having a second thickness greater than the first thickness, and a second peripheral portion between the first peripheral portion and the skirt and having a third thickness greater than the second thickness. The first annular wall extends from the base wall at a juncture of the central and first peripheral portions of the base wall. The second annular wall extends from the base wall at a juncture of the first and second peripheral portions of the base wall. In some preferred embodiments of the disclosure, both of the annular walls have circumferentially continuous axially flexible annular projections that extend toward the opposing wall, most preferably in radial alignment with each other. In another preferred embodiment of the disclosure, the radially inner annular wall is contoured for plug-sealing engagement with the inside surface of the container neck finish when the closure is attached to the container neck finish. In the exemplary preferred embodiments of the disclosure, the annular projections are wedge-shaped in radial cross section.